كتاب النكاح
28
Marriage

Yahya related to me from Malik from Yahya ibn Said that Said ibn al-Musayyab said, "There are three things in which there is no jest:

marriage, divorce, and setting free."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، أَنَّهُ قَالَ ثَلاَثٌ لَيْسَ فِيهِنَّ لَعِبٌ النِّكَاحُ وَالطَّلاَقُ وَالْعِتْقُ ‏.‏
USC-MSA web (English) reference : Book 28, Hadith 56
Arabic reference : Book 28, Hadith 1151